Soil Testing Equipment

Referent and Standards Product for Soil Testing Equipment

Soil: The Living Matrix

Around the world, farmers are very intelligent and know the characteristics of soil. They know many  things about  the soil  that scientists do not, and scientists know many  things  that  farmers  do  not,  so  these  two  groups  of  workers  must  work together. This is true of North American, European, and Asian countries. Farming practices are based on empirical experience; some of these practices may not stand up to scientific testing, but others obviously must do.The importance of soil structure as a factor in soil fertility is becoming increasingly clear. If a plant is to grow, its roots must spread so that their delicate structures of root  hairs  can  get  access  to  plant  nutrients. They  also  only  thrive  if  there  is  an adequate supply of water and air. In several countries with plantations of sugarcane, the continuous high yields obtained through irrigation and the extensive application of manure  and  fertilizers  have  created  problems. Chemical  analyzes  of  the  soils
from such areas show that common plant nutrients are still present, but that something has happened to the soil that is interfering with its productivity. At first it was thought  that  the cane  itself  is deteriorating, but  this  is not  likely, as  it propagates vegetatively.  Instead,  unfavorable  conditions  for  beneficial  soil microorganisms may have been produced. The deterioration of  the  soil  structure  seems  to play a direct part in this, because soil microorganisms have an important influence on the soil structure. Soil organic matter – the formation, decomposition, and transformation of which are caused by microorganisms – is of great importance to sustainable soilfertility and soil structure.

More experiments on soil structure and other physical properties of soils, such as permeability,  porosity,  and  moisture  retention  capacity,  are  desirable.  Soil  fertility depends on a large number of complex factors, not all of which are known. Physical properties of the soil are no less important than chemical properties. The clay fraction determines many physical and chemical properties of soils. The properties of clays are determined by their mineralogical compositions. X-ray studies and differential thermal analyses of clays have now become necessities in soil laboratories. The electrochemical properties of clays are fundamentally important to understanding soil behavior. This chapter introduces the various types of soil and their functions, as well as the pollution of the soil with heavy metals, which is detrimental to the health of the soil

Soil Taxonomy and Classification

A soil  taxonomist distinguishes soils partly on  the basis of  the kind of diagnostic horizon(s)  present  in  each  soil.  The  current  soil  taxonomy  (classification)  was adopted  in 1965; a simplified account of  this classification system follows below(see US Soil Survey Report 1972, 1975). Order. This is the most general category. All soils fit into one of ten orders. Suborder. Suborders within a soil order are differentiated largely on the basis of soil properties  and  horizons  resulting  from  differences  in  soil moisture  and  soil temperature. Forty-seven suborders are presently recognized.
Great group. Soil great groups are subdivisions of suborders. The 185 great groups found in the US, and 225 worldwide, have been established largely on the basis of  differentiating  soil  horizons  and  soil  features.  The  soil  horizons  include those that have accumulated clay, iron, and/or humus, and those that have pans
(hardened or cemented soil  layers)  that  interfere with water movement or root penetration.
Subgroup.  Each  soil  great  group  is  divided  into  three  kinds  of  subgroups:  one representing the central (typic) segment of the soil group; a second that has prop-erties that tend toward other orders, suborders, or other great groups (intergrade group); and a  third  that has properties  that prevent  its classification as  typic or intergrade. About 970 subgroups are known in the United States.Family. Subgroups contain soil families, which are distinguished primarily on the basis of  soil properties  important  to  the growth of plants or  the behavior of soils when  used  for  engineering  purposes. These  soil  properties  used  include texture, mineral  reactions  (pH),  soil  temperature,  precipitation  pattern  of  the area,  permeability,  horizon  thickness,  structure,  and  consistency. About  4,500 families have been identified in the United States.Series. Each family contains several (similar) soil series. The 10,500 or more soil series  in  the United States have narrower  ranges of  characteristics  than  a  soil family. The name of the soil series has no pedogenic (i.e., related to soil formation) significance; instead, it represents a prominent geographic name of a river, town,or area near where the series was first recognized. Soil series are differentiated on  the  basis  of  observable  and mappable  soil  characteristics,  such  as  color, texture,  structure,  consistency,  thickness,  reactions  (pH),  and  the  number and  arrangement  of  horizons  in  the  soil  pedon  as well  as  their  chemical  and
mineralization  properties.  Terms  describing  surface  soil  texture,  percentage slope,  stoniness,  saltiness,  erosion,  and  other  conditions  are  called  phases. Mapping units are created by adding phase names to series names. All mappingunits are polypedons. Prior to 1971, soil type was a mapping unit that was used
to denote a subdivision of a series indicating the series name and surface texture. Soil type is no longer official nomenclature; it has been replaced by series phase.

The  prime  land  means  the  best  land.  The  definition  of  prime  land  will  change depending  on  the  use  of  the  land,  and  full  agreement  as  to  exactly  how  “prime” should be defined  is unlikely, even  for a  specific  land use. For  farmland use,  it  is proposed that prime land should meet all the followingrequirements: adequate natu-ral  rainfall  or  adequate  and  good-quality  irrigation water  for  intended  use; mean annual temperature >32°F (0°C) and mean summer temperature >46°F (8°C); lack of excessive moisture – flooding should not occur more often than once every two years; water table should be below the rooting zone; soil should not be excessively acidic, alkaline, or saline; soil permeability should be at least 0.38″  h−1 (1.0 cm h−1) in  the upper 20″  (51  cm);  the  amount of gravel,  cobbles, or  stones  should not be excessive  enough  to  seriously  interfere  with  power  machinery;  any  restricting layer  in  the  soil  should be deep  enough  to permit  adequate moisture  storage  and unhampered root growth, and; the soil should not be excessively erodible.The objectives of soil surveys and taxonomy are to facilitate growth on soils that have never been grown on before, and  to  learn enough about certain soils  to predict how they would respond when irrigated with a specific quantity of irrigation water of known quality. This objective also emphasizes  the  inclusion of a  rational means of transferring technology from one soil to another, interpretations that allow the predition of land use for every soil mapped, and that the survey should serve as a scientific database.  Soil  surveying  has  developed  into  a  specialized  subject. A  survey  report contains information on not only the characteristics of the soil and its profile, but also the  existing  and potential uses of  the  land,  the yields obtained by  the  farmer or by experimental stations under different systems of management, erosion and drainage conditions, and the potential for reclamation or its suitability for irrigation, where these are necessary. Soil maps and survey reports form the basis for planning the utilization of the land, and they have also been found useful in road and building projects.

Drilling Equipment and Operation - Drilling Muds and Completion Systems. Part 1

Drilling Equipment and Operation - Drilling Muds and Completion Systems

A. Drilling Muds and Completion Systems


1.1.1 Drilling Fluid Definitions and General Functions
Results of research has shown that penetration rate and its response to weight on bit and rotary speed ishighly dependent on the hydraulic horsepower reaching the formation at the bit. Because the drilling fluid flowrate sets the system pressure losses and these pressure losses set the hydraulic horsepower across the bit, it can be concluded that the drilling fluid is as important in determining drilling costs as all other “controllable” variables combined. Considering these factors, an optimum drilling fluid is properly formulated so that the flow rate necessary to clean the hole results in the proper hydraulic horsepower to clean the bit for the weight and rotary speed imposed to give the lowest cost, provided that this combination of variables results in a stable borehole which penetrates the desired target. This definition incorporates and places in perspective the five major functions of a drilling fluid.

1.1.2 Cool and Lubricate the Bit and Drill String
Considerable heat and friction is generated at the bit and between the drill string and wellbore during drilling operations. Contact between the drill string andwellbore can also create considerable torque during rotation and drag during trips. Circulating drilling fluid transports heat away from these frictional sites, reducing the chance of premature bitfailure and pipe damage. The drilling fluid also lubricates the bit tooth penetration through the bottom hole debris into the rock and serves as a lubricant between the wellbore and drill string, reducing torque and drag.

1.1.3 Clean the Bit and the Bottom of the Hole
If the cuttings generated at the bit face are not immediately removed and started toward the surface, they will be ground very fine, stick to the bit,and in general retard effective penetration into uncut rock.

1.1.4 Suspend Solids and Transport Cuttings and Sloughings to the Surface
Drilling fluids must have the capacity to suspend weight materials and drilled solids during connections, bittrips, and logging runs, or they will settle to the low side or bottom of the hole. Failure to suspend weight
materials can result in a reduction in the drilling fluids density, which can lead to kicks and potential of a blowout. The drilling fluid must be capable of transporting cuttings out of the hole at a reasonable velocity that minimizes theirdisintegration and incorporation as drilled solids into the drilling fluid system and able to release
the cuttings at the surface for efficient removal. Failure to adequately clean the hole or to suspend drilled solids can contribute to hole problems such as fill on bottom after a trip, hole pack-off, lost returns, differentially stuck pipe, and inability to reach bottom with logging tools. Factors influencing removal of cuttings and formation sloughings and solids suspension include.

• Density of the solids
• Density of the drilling fluid
• Rheological properties of the drilling fluid
• Annular velocity
• Hole angle
• Slip velocity of the cuttings or sloughings

1.1.5 Stabilize the Wellbore and Control Subsurface Pressures
Borehole instability is a natural function of the unequal mechanical stresses and physical-chemical interactions and pressures created when supporting material and surfaces are exposed in the process of drilling a well. The drilling fluidmust overcome the tendency for the hole to collapse frommechanical failure or fromchemical interaction of the formation with the drilling fluid. The Earth’s pressure gradient at sea level is 0.465 psi/ft,
which is equivalent to the height of a column of salt water with a density (1.07 SG) of 8.94 ppg.
In most drilling areas, the fresh water plus the solids incorporated into the water from drilling subsurface formations is sufficient to balance the formationpressures.

However, it is common to experience abnormallypressured formations that require high-density drilling fluids to control the formation pressures. Failure to control downhole pressures can result in aninflux of formation fluids, resulting inakick or blowout. Borehole stabilityis also maintained or enhanced by controlling the loss of filtrate to permeble formations and by careful control of the chemical composition of the drilling fluid. Most permeable formations have pore space openings too small to allow the passage of whole mud into the formation, but filtrate from the drilling fluid can enter the pore spaces. The rate at which the filtrate enters the formation depends on the pressure differential between the formation and the column of drilling fluid and the quality of the filter cake deposited on the formation face. 

Large volumes of drilling fluid filtrate and filtrates that are incompatible with the formation or formation fluids may destabilize the formation through hydration of shale and/or chemical interactions between components of the drilling fluid and the wellbore. Drilling fluids that produce low-quality or thick filter cakes may alsocause tight hole conditions, including stuck pipe, difficulty in running casing, and poor cement jobs

1.1.6 Assist in the Gathering of Subsurface Geological Data and Formation Evaluation

Interpretation of surface geological data gathered through drilled cuttings, cores, and electrical logs is used to determine the commercial value of the zones penetrated. Invasion of these zones by the drilling fluid, its filtrate (oil or water) may mask or interfere with interpretation of data retrieved or prevent full commercial recovery of hydrocarbon.

1.1.7 Other Functions
In addition to the functions previously listed, the drilling fluid should be environmentally acceptable to the area inwhich it is used. It should be noncorrosive to tubulars being used in the drilling and completion operations.
Most importantly, the drilling fluid should not damage the productive formations that are penetrated. The functions described here are a fewof themost obvious functions of a drilling fluid. Proper application of drilling fluids is the key to successfully drilling in various environments.


Ageneralized classification of drilling fluids can be based on theirfluid phase, alkalinity, dispersion, and type of chemicals used in the formulation and degrees of inhibition. In a broad sense, drilling fluids can be broken into five major categories.

1.2.1 Freshwater Muds—Dispersed Systems
The pHvalue of low-pHmudsmay range from7.0 to 9.5. Low-pHmuds include spud muds, bentonite-treated muds, natural muds, phosphate treated muds, organicthinned muds (e.g., red muds, lignite muds, lignosulfonatemuds), and organic colloid–treatedmuds. In this case, the lack of salinity of the water phase and the addition of chemical dispersants dictate the inclusion of these fluids inthis broad category.
1.2.2 Inhibited Muds—Dispersed Systems
These are water-base drilling muds that repress the hydration and dispersion of clays through the inclusion of inhibiting ions such as calcium and salt. There are essentially four types of inhibited muds: lime muds (high pH), gypsummuds (lowpH), seawatermuds (unsaturated saltwater muds, lowpH), and saturated saltwatermuds (lowpH).Newer-generation inhibited-dispersed fluids offer enhanced inhibitive performance and formation stabilization; these fluids include sodium silicate muds, formate brine-based fluids, and cationic polymer fluids.

1.2.3 Low Solids Muds—Nondispersed Systems
These muds contain less than 3–6% solids by volume, weight less than 9.5 lb/gal, and may be fresh or saltwater based. The typical low-solid systems are selective flocculent, minimum-solids muds, beneficiated clay muds, and low-solids polymer muds. Most low-solids drilling fluids are composed ofwaterwith varying quantities of bentonite and a polymer. The difference among low-solid systems lies in the various actions of different polymers.
1.2.4 Non aqueous Fluids
Invert Emulsions Invert emulsions are formed when one liquid isdis persed as small droplets in another liquidwith which the dispersed liquidis immiscible. Mutually immiscible fluids, such as water and oil, can be emulsified by shear and the addition of surfactants. The suspending liquid is called the continuous phase, and the droplets are called the dispersed or discontinuous phase. There are two types of emulsions used indrilling fluids: oil-in-water emulsions that have water as the continuous phase and oil as the dispersed phase and water-in-oil emulsions that have oil as the continuous phase andwater as the dispersed phase (i.e., invert emulsions) Oil-Base Muds (nonaqueous fluid [NAF]) Oil-base muds containoil (refined from crude such as diesel or synthetic-base oil) as the continuous phase and trace amounts of water as the dispersed phase. Oil-base muds generally contain less than 5% (by volume) water (which acts as a polar activator for organophilic clay), whereas invert emulsion fluids generally have more than 5% water in mud. Oil-base muds are usually a mixture of base oil, organophilic clay, and lignite or asphalt, and the filtrate is all oil.


To properly control the hole cleaning, suspension, and filtration properties of a drilling fluid, testing of the fluid properties is done on a daily basis. Most tests are conducted at the rigsite, and procedures are set forth
in the API RPB13B. Testing of water-based fluids and nonaqueous fluids can be similar, but variations of procedures occur due to the nature of the fluidbeing tested.
1.3.1 Water-Base Muds Testing
To accurately determine the physical properties of water-based drilling fluids, examination of the fluid is required in a field laboratory setting. In many cases, this consists of a fewsimple tests conducted by the derrickman or mud Engineer at the rigsite. The procedures for conducting all routine drilling fluid testing can be found in the American Petroleum Institute’s API RPB13B.

within ±0.1 lb/gal or ±0.5 lb/ftDensity Often referredto as themudweight,densitymay be expressedas pounds per gallon (lb/gal), pounds per cubic foot (lb/ft3), specific gravity (SG) or pressure gradient (psi/ft). Any instrument of sufficient accuracy 3 may be used. The mud balance is the instrument most commonly used. The weight of a mud cup attached to one end of the beam is balanced on the other end by a fixed counterweight
and a rider free to move along a graduated scale. The density of the fluid isadirect reading from the scales located on both sides of the mud balance.

Marsh Funnel Viscosity Mud viscosity is a measure of the mud’s resis- tance toflow.Theprimary function ofdrillingfluidviscosity is a to transport cuttings to the surface and suspend weighing materials. Viscosity must
be high enough that the weighting material will remain suspended but low enough to permit sand and cuttings to settle out and entrained gas to escape at the surface. Excessive viscosity can create high pump pressure, which magnifies the swab or surge effect during tripping operations. The control of equivalent circulating density (ECD) is always a prime concern when managing the viscosity of a drilling fluid. The Marsh funnel is a rig site instrument used tomeasure funnel viscosity. The funnel isdimensioned so that by following standard procedures, the outflow time of 1 qt (946ml) of freshwater at a temperature of 70±5◦F is26±0.5 seconds A graduated cup is used as a receiver.
Direct Indicating Viscometer This is a rotational type instrument powered by an electricmotor or by a hand crank .Mud is contained in the annular space between two cylinders. The outer cylinder or rotor sleeve is driven at a constant rotational velocity; its rotation in the mud produces a torque on the inner cylinder or bob. A torsion spring restrains the movement of the bob. A dial attached to the bob indicates its displacement on a direct reading scale. Instrument constraints have been adjusted

so that plasticviscosity, apparent viscosity, and yield point are obtained by using readings from rotor sleeve speeds of 300 and 600 rpm. Plasticviscosity (PV) in centipoise is equal to the 600 rpm dial reading minus the 300 rpm dial reading. Yield point (YP), in pounds per 100 ft 2, is equal to the 300-rpm dial reading minus the plasticviscosity. Apparent viscosity in centipoise is equal to the 600-rpm reading, divided by two.

Gel Strength Gel strength is a measure of the inter-particle forces and indicates the gelling thatwill occurwhen circulation is stopped. This property prevents the cuttings from setting in the hole. High pump pressure is generally required to “break” circulation inahigh-gel mud. Gel strength is measured inunits of lbf/100 ft 2.This reading is obtained by noting the maximum dial deflection when the rotational viscometer is turned at a low rotor speed (3 rpm) after the mud has remained static for some period of time (10 seconds, 10 minutes, or 30 minutes). If the mud is allowed to remain static in the viscometer for a period of 10 seconds, the maximum dial deflection obtainedwhen the viscometer is turned on is reported as the initial gel on the API mud report form. If the mud is allowed to remain static for 10minutes, themaximumdial deflection is reported as the 10-min gel. The same device is used to determine gel strength that is used to determine the plasticviscosity and yield point, the Variable Speed Rheometer/Viscometer. 

API Filtration Astandard API filter press is used to determine the filter cake building characteristics and filtration of a drilling fluid(Figure 1.4). TheAPI filter press consists of a cylindricalmud chambermade ofmaterials resistant to strongly alkaline solutions.Afilter paper is placed on the bottom of the chamber just above a suitable support. The total filtration area is 7.1 (±0.1) in. 2. Below the support is a drain tube for discharging the filtrate into a graduated cylinder. The entire assembly is supported by a stand so 100-psi pressure can be applied to the mud sample in the chamber.At the end of the 30-minute filtration time, the volume of filtrate is reported as API filtration. inmilliliters. To obtain correlative results, one thickness of the proper 9-cm filter paper—Whatman No. 50, S&S No. 5765, or the equivalent—must be used. Thickness of the filter cake is measured and reported in 32nd of an inch. The cake isvisually examined, and its consistency is reported using such notations as “hard,” “soft,” tough,” ’‘rubbery,” or “firm.”

Sand Content The sand content indrilling fluids is determined using a 200-mesh sand sieve screen 2 inches indiameter, a funnel to fit the screen, and a glass-sand graduated measuring tube (Figure 1.5). The measuring
tube is marked to indicate the volume of “mud to be added,” water to be added and to directly read the volume of sand on the bottom of the tube.Sand content of themud is reported in percent by volume.Also reported is thepoint of sampling (e.g.,flowline, shale shaker, suctionpit). Solids other than sandmay be retained on the screen (e.g., lost circulationmaterial), and the presence of such solids should be noted.

Liquids and Solids Content A mud retort is used to determine the liquids and solids content of a drilling fluid.Mud is placed in a steel container and heated at high temperature until the liquid components have been
distilled off and vaporized (Figure 1.6). The vapors are passed through a condenser and collected in a graduated cylinder. The volume of liquids (water and oil) is then measured. Solids, both suspended and dissolved, are determined by volume as a difference between the mud in container and the distillate in graduated cylinder. Drilling fluid retorts are generally designed to distill 10-, 20-, or 50-ml sample volumes